Conventional millimeter wave oscillators use a high frequency device, such as a Gunn or impatt diode, which oscillates in a metal cavity. In the frequency range of 35 GHz to 300 GHz, there are numerous applications for local oscillators for receivers and transmit/receive functions in radar such as self oscillating mixers. Since such applications are typically low power, it would be highly desirable to obtain these oscillators at low cost. Unfortunately, the high operating frequencies with their attendant short wavelengths requires ultra precision machining so that a reliable metal cavity oscillator for this frequency range may cost generally on the order of three thousand dollars which severely limits its use to only those applications economically justifiable.
Since dielectric waveguides employ evanescant transmission modes for the E and the H fields, precision boundaries are not required for the dielectric waveguides as is required for metal boundaries or walls. However, there are a number of difficulties in the deployment of dielectric waveguides. Although the loss is negligible in passive dielectric transmission lines, there is a power loss in the region of the oscillator due to leakage radiation. Typically, there is little or practically no tuning capacity. The presence of these deficiencies renders known dielectric arrangements low in power output, generally at output one milliwatt.
It is a primary object of this invention to provide a low cost millimeter wave oscillator having a simplified circuit package with good power output capability.
It is a related object to provide a millimeter wave oscillator wherein dimensions are not critical.
Another object of the invention is to increase the coupling efficiency between an oscillating device and a passive dielectric transmission line at a desired frequency with nearly fixed impedance so that required tuning is minimized.
A still further object is to provide a low cost millimeter wave oscillator which may be tuned, if desired, to provide a certain latitude of flexibility.